Sunday, April 23, 2006

Chalmers, Dennett, and the Zombies

I have been rereading David Chalmers' The Conscious Mind, which puts forward the strongest possible case for mind-body dualism. I enjoy reading Chalmers more than any other contemporary philospher except for Dennett and Rorty, and greatly admire his intellectual honesty and clarity of thought. However, I find much more convincing Dennett's theory that consciousness is just a functional property of a highly complex information-processing system such as the brain, than Chalmers elegant defense of dualism. One thing I will try to do in this post is articulate why I am not persuaded by Chalmers.

The most striking thing about Chalmers' view of mind is how close to Dennett's it is in many respects. Contra Searle and other doubters, he argues for a strong form of AI in which any computer, what's more, every physical system that is an implementation of a suitable program (the one neurons in the brain implement, for example) will become conscious. The only point of disagreement with Dennett (except from some minor quibbles) is that for Dennett the conscoiusness is the information processing (IP), while for Chalmers consciousness is an extra fundamental feature of the world, correlated with the IP by contingent laws of nature akin to the fundamental laws of physics. This is the difference which Chalmers makes between "reductive" (bad) and "nonreductive" (good) functionalism.

But what is the cash value of the distinction? If it walks and quacks like a duck, it is a duck. If all and only all IP systems of a certain kind instantiate consciousness, the natural instinct of any scientist will be to apply Occam's Razor and say that consciousness just is the IP. It makes for a simpler worldview, makes science more unified (consciousness doesn't look like the kind of entity that appears in other fundamental physical laws), and dissolves all the paradoxes about epiphenomenalism and phenomenal judgements that trouble Chalmers.

Chalmers would protest that this is "not taking consciousness seriously". The connection between consciousness and IP is natural, not conceptual. One can imagine (concieve, in Chalmers' wording) beings with all the usual IP going on that a normal brain has but with no real, first-person point of view consciousness. This is the (in?)famous "zombie argument", which Chalmers coaches in a lot of modal terminology (possible worlds, primary and secondary intensions, and the like; Richard Chapell has a series of recentposts explaining these concepts). Dennett finds the argument ridiculous and preposterous, but his refutations are less than convincing, because he doesn’t touch what in my opinion are the deep sources of the disagreement between Chalmers and him.

Scientists would, in my opinion, not buy the zombie argument because they see little use for a distinction between a "conceptual" and a "nomological" necessitation of consciousness by physical facts. Is mass conceptually defined as a form of energy, or a distinct thing only nomologically correlated to it? It doesn't matter; as long as we agree in the pysical predictions made this is only a pragmatical question on how to axiomatize pysics. A 19th century pysicist would probably be able to "concieve" mass with no energy; does this prove anything? No; our concepts change and evolve with the growth of scientific knowledge; what is concievable now may become unconcievable later and vice-versa. Concepts are just tools for describing the world, and we can change them and reform them if we need to.

This picture of science, familiar since Quine, is pressupposed by Dennett, but implicitly rejected by Chalmers. When he talks of adding consciousness to the list of fundamental physical properties of the world, and adding the IP-consciousness correlation laws to the list of fundamental laws of nature, he overlooks that physics (despite common talk, even by physicists, even sometimes by me on behalf of convinience) does not provide a list of fundamental properties and a list of fundamental laws. It may provide a fundamental theory or a list of them (currently, they would be the Standard Model + Quantum Field Theory, and General Relativity, although we know that is not the end of the story as quantum gravity is left out) but not a list of fundamental entities the world is made of with a list of contingent laws of nature holding between them. What an entity such like the electromagnetic field is, is defined by what laws of nature it obeys and therefore by its relations with other entities. We can choose to make some features definitional and some others nomological, but that is mostly a matter of convinience and is subject to possible change in light of new knowledge. (This is, by the way, the reason I dislike the ubiquitous talk of “possible worlds” to frame philosophical questions. What counts as a possible world depends on the concepts used to describe them, which are subject to change with scientific progress.) Dennett himself makes the point when (addressing other thought experiments different from the zombie argument, but similar in style) he says:

Smiling demons, cow-sharks, Blockheads, and Swampmen are all, some philosophers think, logically possible, even if they are not nomologically possible, and these philosophers think this is important. I do not. Why should the truth-maker question cast its net this wide? Because, I gather, otherwise its answer doesn't tell us about the essence of the topic in question. But who believes in real essences of this sort nowadays? Not I.

I suspect Chalmers could agree with this with respect to all scientific concepts except consciousness. He would say that the concepts of phenomenal red or of pain cannot be subjected to the redefinitions possible for other scientific concepts. Our knowledge of them is by their intrinsic features (it is essential to pain, that it feels painful, while any functional properties of the state "being in pain" are not essential). This is the way Rorty characterizes the similar disagreement between Nagel and Dennett in his masterful essay "Holism, Intrinsicality, and the Ambition of Trascendence" (for Dennett and his critics). But this shows that all the zombie arguments are question-begging, because to carry any force they must assume that there is something very special about consciousness that distinguishes it from other subjects for science in the first place. A Dennettian would simply deny that the scientific description of consciousness requires concepts different in nature to those used in other areas.

To summarise, we can imagine a dialogue beetween Chalmers and Dennett to proceed like this:

C: We can concieve of zombies, therefore physics and IP do not conceptually entail consciousness, therefore consciousness is not identical to physical IP, even if it is universally correlated with it.

D: But if the correlation is indeed universal, then we better redefine our concept of consciousness to make it identical with physical IP and have a simpler scientific picture.

C: We cannot do that, because our present concept of consciousness captures intrinsic features of it, which cannot be done away with by redefinition.

D: This kind of intrinsic grasp on a concept does not exist anywhere else in science. To assume it does exist for phenomenal concepts is question-begging, because it makes from the start consciousness different from all other things.

Of course, this does not refute Chalmers' dualism; it merely shows that there is no non-circular agument for it. Dennett can still acknowledge the powerful tug of what he calls The Zombie Hunch as an "intuition", while going on to argue that reasons of scientific progress such as simplifying and clearing of "mysteries" our picture of the world speak in favour of not listening to that intuition.

If you want to know more about zombies and their use in philosophy, this resource page is the right place to go.

43 Comments:

Hi. I'm enjoying discovering your blog, which I found via a search on Rovelli's RQM which turned up your recent post.

"This kind of intrinsic grasp on a concept does not exist anywhere else in science". Well, I would say yes, of course. The existence of first-person experience underlies everything we do, including the intersubjective discipline of science. One cannot use the third-person concepts of science to explain first-person experience. Should we care about this? I would say yes, philosophically or metaphysically we should certainly care, and think about what it means. Scientifically, I'm less sure (I'm not a scientist). On the other hand I'm continually tempted to see a role for experience at the micro-physical level (in approaches to the quantum measurement problem like Rovelli's).Best regards, - Steve Esser

Hi Steve. I had noticed your blog some time ago, but never got around to link to it. Next time I update my blogroll I'll include it. Thanks for commenting!

For me, the assertion "One cannot use the third-person concepts of science to explain first-person experience" seems quite unwarranted. There is certainly a prima facie "intuition" that many people share in this respect. But I think that the detailed "third-person" theories put forward by Dennett and other philosophers and cognitive scientists can help us overcome this intuition and eventually understand consciousness without revolutionizng our worldview. I certainly do not know of any compelling argument to support the "irreducible first-person" view -the zombie argument and the Mary argument are either just restatements of the intuition, or fail for the reason outlined in the post.

I understand your objection that it is an intuition rather than an argument. To me, however, there is a kind of negative argument of the reductio ad absurdum type: the claim that first person experience completely reduces to non-experiential components would eliminate from its worldview the thing we have the best direct knowledge of - our experience.

You say: "...the claim that first person experience completely reduces to non-experiential components would eliminate from its worldview the thing we have the best direct knowledge of -our experience."

But why? To reduce is not to eliminate. I agree that experience is what we have best knowledge of, but that doesn't imply that it cannot be understood fully from the third person. That is a strong philosophical claim that goes far beyond what is "indubitable" in an experience. Compare:

a) I have now an experience of green.

b) I have now an experience of green, which captures an intrinsic property of "greeness" impossible to define and explain in functional or physical third-person terms.

The claim a) seems to me as strong knowledge as we can have of anything, but the claim b) is very much open to doubt. And if you say that the very concept of "experience" implies b) because it is essentially first-personal, I would say that this concept of experience is open to revision, which would lead to redescribe a) without making it less certain. Compare with Dennett's thought experiment about a community which speaks of "having fatigues" instead of "being tired" and think it is indubitable that they have fatigues.

Thanks - I appreciate the opportunity for the debate. Let me try to respond (although I don't recall that particular Dennettian thought experiment).

I don't think I need claim 'b'. "Qualia" disconnected from first person experience are easier to try to explain (which is why Dennett focuses more on them). I would like to keep the focus on "a". I want an explanation of what it is about a natural system which entails that it has first-person experience. I argue that a typical third-person physical explanation will not provide an explanation.

In usual cases you can reduce without eliminating a phenomenon, because there is some property of the parts by which we can understand why the higher order phenomenon emerges. In the case of experience, if you reduce it to non-experiential parts there is nothing in the parts by virtue of which the phenomenon can be said to emerge.

This is beautifully written, and actually makes me respect Chalmers a bit more. In the end, I have little patience with dualism, which tends to break down to pretty much dormitive virtue. But to come so close to a pragmatic view, yet in the end be unable to relinquish the idea that consciousness is something special... well, in that context it reads more like human frailty than bad philosophy. Reminds me of some of the 19th-century natural philosophers -- "Of course I support this Darwin fellow, but there must be just a little inheritance of acquired characteristics, right?"

Jess -I feel a little like you with respect to Chalmers. I certainly agree that he is not a bad philosopher -in fact, I think he is an extraordinarly good one. He articulates in a very clear and fair-minded way the basic intuitions behind dualism, and draws the all the logical consequences from them on while remining consistent with science. He just can't bring himself to realize that those intuitions are not forced upon us.

(On the other hand Searle at least in the area of philosophy of mind strikes me as a particularly bad philosopher. This judgement might be presumptuous in an amateurish outsider like me, but I can't help it).

Steve -thanks for your continuing feedback! Your focus on the problem of the "first-person" character of experience is interesting. I don't think it is such a difficult nut to crack for functionalism as the apparent intrinsicness of qualia is. The "self" itself (sorry for the pun!) is not observable, as Hume noted, and the "feeling" of self and "point of view" in experiences can perhaps be accounted for in terms of a set of dispositions, memories, and other functionally analyzable processes. I admit that I don't know of any fully satisfactory account of this kind (Dennett's included) but I don't see any reason to think it impossible.

Well, at least there are two amateurish outsiders who think Searle is a bad philosopher. Then again, I am basing my opinion partly on a former philosophy of mind friend, so... two amateurish outsiders and a secondhand professional opinion?

The thing that really tickles me about Searle is that the Chinese Room is one of my favorite arguments for the possibility of artificial intelligence. Searle argues that the fact that the correct answers are coming out of the room doesn't mean he knows Chinese. No, of course not. The room knows Chinese.

Jess - I think the Chinese Room is a poor model for something that understands a language. For one thing, it doesn't learn, it's state is not changed by a question/answer exchange, so the next question cannot refer back, no coherent conversation is possible. CR is a lookup table, and interacting with it would have the feel of interacting with a lookup table, not the feel of interacting with an entity that understands language or anything else. Searle's suggestion that anything that is computable is equivalent to a static lookup table is flawed. CR is not a good argument for a or against anything interesting. (But we're getting off topic.)

It may depend of which version of the Chinese Room experiment you consider, but my understanding is that the experiment assumes that the Room can pass the Turing Test. If so I think the program that generates the answers must be able to "learn" and cannot be structured as a simple lookup table. (It is one from the point of view of the guy inside the room implementing the program, but that is not the relevant point of view to take. As Jess says, it is the room that speaks Chinese.)

I have read the paper you mention about zombies, and found it quite persuasive, although ultimately I think not much rests on whether zombies are "conceivable". It may be true that Chalmers can conceive of a zombie using his present conceptual framework, but he may profit by changing to one in which he can't.

I certainly agree that if the CR demonstrates mastery of Chinese (or any other intelligent behaviour), the capability must be ascribed to the system as a whole, not to the human executing a mechanical task. Searle himself anticipates this reaction to his thought experiment and calls it the "system reply". It has been discussed at length by Hofstadter, Dennett and many others, and personally I think that Searle's response to the "systems reply" ("What if the human memorizes the entire lookup table: Now does he understand Chinese?") - and indeed his entire conclusion from the CR thought experiment - has been thoroughly refuted.

What I was trying to say above was that while I agree with Jess that CR is not a very convincing argument against AI, I don't see how it could be used as a good argument for the possibility of AI either. I imagine the argument would go: "The room is intelligent, and the human performs a purely mechanical task. We can replace the human with a simple device and voila! we have an intelligent machine." But surely the trick is to write the software (the rules that the human in the CR uses), and there is (obviously) nothing in Searle's paper that suggests how to do this. Put another way: Searle in effect says "Suppose we could build a machine that speaks Chinese..." and then goes on to discuss whether such a machine should be said to "understand Chinese". I don't think there is anything in the thought experiment that could be taken as a proof that it is in fact possible to build a machine that speaks Chinese.

I do think that the zombie argument is very important for Chalmers' dualism. The "fact" that a zombie is "logically possible" or "conceivable" is the only evidence he presents to support the thesis that experience cannot be physically explained. We can imagine a zombie-Chalmers - so the argument goes - where everything physical/functional is identical to the real Chalmers, and they behave identically, but zombie-Chalmers has no subjective experience. Because the physical goings-on in zombie-Chalmers do not cause consciousness, the consciousness in real-Chalmers must have some extra-physical explanation. If the zombie thought experiment breaks down under pressure (as I think it does), then what is the evidence against materialism?

Chalmers also uses thought experiments like "dancing qualia" and "inverted qualia". I think these are variations of the zombie idea, and they also break down under pressure. Consider the inverted qualia thought experiment: the possibility that your experience of red is like mine of green and vice versa. In other words, red things "look" to you like green things "look" to me. A variation (described by Chalmers) is the single-person inverted-qualia fantasy: you wake up one morning having "green experience" when looking at red things and vice versa. The argument is again that functionally everything is the same, but the "experience" is different. Again, I don't think this is possible to imagine: When we imagine waking up with inverted qualia, I think we would imagine ourselves exclaiming something like "Wow! The trees are all red!", which shows that what has changed is functional. This is easier to see if we imagine that only the quale associated with green stimulus has changed, so that green and red now "look" the same. I would claim that it is not possible to imagine still having the functional ability to distinguish colors ("Wow! The trees are still green (I can see that), yet they now look red to me!") Critics of Dennett's third-person "heterophenomenology" method argue that he confuses subjects' beliefs about their experiences with the experiences themselves. I think a thought experiment like the one just described shows that such a distinction is absurd.

I am not a philosopher but to me it seems that an experience and the quale that is associated with it, like seeing red and feeling the redness are two distinct things. The reason I believe so is because for example, when looking for a word whose meaning you know but syntax you forgot, the way you retrieve the word in your brain is by focusing on the quale associated with the meaning of the word. Any word belonging to the class of synonyms fitting the meaning will do. In this case, the quale comes first and the word is simply an external representation of that inner knowledge that the quale represents. In the same way, feeling the redness of the red color is simply to find similarities between or associate a quale whose inner knowledge you have prior to seeing red with the red color. If you change the color of the trees to become red, they will less likely be relaxing to watch during the Sunday picnic since red is more often associate with a vibrant or aggressive color than green. However, if you also invert the quale, then red will become quite relaxing, even though you will see red and not green.

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Thoughts on physics, maths, science, philosophy, and anything else that may cross my mind, plus news about my current life for distant friends, by an Argentinian in the second third year of his PhD at the University of Nottingham.

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